The guys are doing a tech/range session this weekend...there'll be plenty of gas rifles there. I'll see if they can't put up some standard targets (probably just a letter sheet of paper) and pace off the range.
I do notice that the effective range of my gas rifles is less than that of my other electric rifles. And I know that it's due to the hopup rubber. There's very little there to put a lot of hop on BBs. I can get decent range out of it (I'm horrible with distances so I won't guess at this point).
For me...it's gameable (otherwise I wouldn't use it). I shoot within it's effective range (i.e. where I know I'll have a high probability to hit)...and haven't found it too lacking. Lacking only in that I'd love to always have the range and accuracy I get off a PTW.
As with any gas gun...if you slow the recoil down (i.e. put a stiffer spring in there....or make the bolt heavier, which in essence you're doing)...you'll use more gas on the recoil cycle of the system. However, maybe not an issue having swapped out the lead for paper. Dunno.